Deuterium lamps produce broad-band ultraviolet radiation by maintaining a stable electric arc in a deuterium atmosphere. The spectral distribution of this radiation has a continuous range that extends from 160 to 400 nm. This continuous and stable characteristic of the arc makes deuterium lamps a useful source of ultraviolet light for analytical instruments, including spectrophotometers, liquid chromatography detectors, medical analyzers, pollution analyzers, calorimeters, densitometers, and the like.
Basically, deuterium lamps have a cathode and an anode arranged within an evacuated glass envelope that contains deuterium gas. A small restricting orifice is positioned in front of the anode to restrict the flow of current. When operated, a stream of thermoelectrons flows from the cathode toward the anode, thereby forming a "ball of fire" adjacent the anode. This "ball of fire" produces light in the ultraviolet range.
To this end, it has been known to provide a baffle adjacent the anode to shape and direct the light output from the lamp. Heretofore, this baffle was in the shape of a cylindrical segment, with a spherical recess positioned adjacent the aperture. Moreover, the surface of this baffle that faced the "ball of fire" was highly polished and highly reflective.
The particulars of such prior art lamps are shown and described in a catalog, "Deuterium Lamps and Power Supplies for UV Analytical Instruments", Imaging & Sensing Technology Corporation, Horseheads, New York 14845 (undated) and in U.S. Pat. No. 5,552,669. The aggregate disclosures of these two references are hereby incorporated by reference with respect to the background and operation of such deuterium lamps. In the '669 patent, the baffle of interest is indicated at 28, and is described as being a "opening limit plate" welded to focusing electrode 26. Upon information and belief, the shape and surface configuration of such prior art baffles contributed to the formation of certain undesirable interference rings in the output light pattern of such prior art lamps.
Accordingly, it would generally be desirable to eliminate such interference ring(s) from the output light pattern of a deuterium lamp, and to have the light intensity vary as a substantially-continuous inverse function of the distance from the centerline of the aperture.